Tragic accidents by midair collision of aircraft have frequently occurred everywhere in the world. We have often been shocked to hear that near miss has occurred, though midair collision has not occurred fortunately.
In a conventional surveillance radar system, based on air traffic control information obtained from various kinds of radars, multiple range rings indicating a distance from a reference point on a runway on a ground surface, the symbols indicating aircraft under air traffic control, the data tag indicating the data including the flight number, the velocity and the altitude of the aircraft, and a lead line indicating relationships between the symbol and the data tag are displayed in two dimensions on a display screen, while the displayed status is renewed at certain cycles (scan cycles). And a controller has watched the display position of a symbol and learned the contents of a data tag to perform air traffic control. In other words, in the conventional air traffic control method, the position of aircraft, which actually exists in three dimensions, is displayed in a visually recognizable form by a symbol only in terms of position in an XY plane. The position of the aircraft in a Z axis direction, i.e., the altitude of the aircraft is displayed by a numerical value. Therefore, when the controller performs air traffic control work, he or she needs to combine the visually recognizable symbol and the altitude represented by the numerical value so as to image the flight status of the aircraft and needs to perform required air traffic control work, imaging the flight status. He or she needs to have a great deal of experience and make much effort before he or she can accurately image the flight status based on the position of the symbol and the numerical value. When multiple aircraft exist in an air traffic control area, there is a possibility that he or she incorrectly images the flight status since he or she bears a heavy burden. There is a possibility that his or her incorrect image causes near miss or midair collision.
Some technologies to avoid the occurrence of near miss or midair collision of aircraft are listed in JP-A-2000-155900, which is to predict the approach to or collision with of an aircraft the ground. More specifically, three-dimensional elevation data of the terrain of an air traffic control area are stored, an estimated arrival range of the aircraft is set up based on the position and the velocity vector of the aircraft, a finite difference vector is found based on the position of the aircraft and the elevation data, and it is determined based on the finite difference vector and the velocity vector of the aircraft whether the above-mentioned elevation data are in the estimated arrival range of the above-mentioned aircraft.    (1) JP-A-3-40200 discloses a technique wherein the first aircraft is displayed in its own altitude plane, displayed apparently in three dimensions on a display screen therein, and a mark indicating the second aircraft that has been approaching to the first aircraft is displayed at a position on the display screen so as to correspond to the three-dimensional position of the second aircraft. However, it is impossible to comprehensively and visually grasp relative relationships such as the positions, the velocities and the travel directions of plural aircrafts at an air traffic control console with this technique.    (2) A system wherein the flight trajectory of aircraft is displayed in a three-dimensional reduced model space of an area surrounding an airport on a display screen based on aircraft position data detected by a radar system in air traffic control is disclosed in JP-A-8-110380.
However, in this technique, although it is possible to display the flight trajectories and the current positions of respective aircraft to a certain terrain, it is impossible to display relative relationships, such as the velocities, the travel directions, the inter-distance and the changing statuses of the respective aircrafts.    (3) JP-A-9-304526 discloses a technique wherein in order to visually recognize the positions, the velocities, the travel directions, the attitudes and the like of aircraft, a plane containing a reference point on a runway extending in substantially parallel with the ground surface is displayed as a reference plane apparently in three dimensions on a display screen, and the aircraft marks indicating of the respective aircrafts, the projection marks of the respective aircrafts projected onto the reference plane, the altitude vectors indicating the altitudes of the respective aircraft, the velocity vectors indicating the velocities of the respective aircraft and the trail vectors indicating the flight trajectories of the respective aircrafts are displayed apparently in three dimensions in a method for displaying air traffic control information. Although it is possible to grasp the positions, the altitudes, the velocities, the travel directions and the flight trajectories of the respective aircraft apparently in three dimensions with this technique, it is difficult to accurately and visually grasp relative relationships between the respective aircraft, in particular the distance and the changing status between the respective aircraft. It is impossible to visually grasp which one of neighboring aircraft a controller should pay more attention to and how much attention he or she should pay if caution is needed.
As explained, with the conventional techniques, it is difficult to predict the possibility of near miss or collision between aircraft in order to avoid the occurrence of the near miss or collision by comprehensively and visually grasping relative relationships between flying aircrafts including the distance between aircraft, the changing status in the distance between aircraft, and the travel directions of the respective aircraft.
There has been not proposed a display method for air traffic control, which is effective to display the flight status of aircraft under air traffic control on a display screen of a display system to grasp these items in order to avoid the occurrence of near miss or collision between aircraft.